This invention relates to nucleic acid hybridization assays.
Such assays are well-known, and are becoming increasingly important in the diagnosis of a wide variety of medical disorders. Typically, a labeled, single-stranded DNA probe which is at least partly homologous with the DNA or RNA of interest is reacted with the denatured nucleic acid of a sample suspected of containing the DNA or RNA of interest. Labeled hybrid complexes indicate the presence of such DNA or RNA.
Probes can be labeled in any of a variety of ways. Some labeling methods are direct, i.e., the label, which is bonded to the probe is itself detectable; examples are radioactive isotopes. Other labels are indirect, i.e., the label is not itself detectable until it undergoes one or more reactions following hybridization; an example is a compound such as biotin, a label which is not itself detectable, but becomes detectable after it reacts with avidin bound to a detectable chemical entity such as a fluorophore.
For convenience, the term "label", as used herein, refers to directly detectable entities such as radioactive isotopes, as well as to indirectly detectable entities such as biotin. The entity, e.g., avidin, to which an indirectly detectable entity bonds to become detectable, is referred to herein as an "indicator".